1. Field of the Invention
This invention relates in general to rock bits used for earth boring, and in particular to improvements in the sealing system for such bits.
2. Description of the Prior Art
U.S. Pat. No. 4,375,242, which issued to Edward M. Galle on Mar. 1, 1983, shows a rock bit which contains a journal or friction bearing and a pressure lubrication system to provide lubricant to the rotatable cutter and supporting shaft. A seal, preferably an O-ring, is provided between the cutter and shaft to retain lubricant within the bearing. An annular groove is formed between the cutter and the leg, adjacent to, but exterior of, the annular seal, for connection with the interior of the bit to provide air flow around the O-ring to cool the ring and to protect the ring from abrasive material. A lubricant pressure system has a movable element, one side of which communicates with the interior of the bit, such that the pressure of the air biases the movable element and lubricant toward the bearing and maintains a positive pressure within the bearing.
Environmental concerns necessitate the introduction of water into the air circulated through the bit. Furthermore, it is not uncommon for the bit to encounter water from other sources, such as ground or surface water, while drilling. This water mixes with the fine rock particles produced by the bit to form a mortar-like substance which can enter and plug the annular groove, especially when the flow of air to the bit is stopped and the bit is not removed from the hole. Once the annular groove is plugged, the air can no longer circulate through the annular groove and cool the seal.